1. Field of the Invention
This invention relates to semiconductor devices and manufacturing methods of a semiconductor devices, and more particulaly to a semiconductor device using a radio-frequency current and a manufacturing method of such semiconductor devices.
2. Description of the Prior Art
Conventional semiconductor devices, as shown in FIG. 1, respectively have an isolation film 3a which selectively has a contact opening 2 on a semiconductor substrate 1 having a diffusion layer 1a, a first layer wiring which is made of gold 4 having titanium-tungsten 6 and platinum 5 in this order from the bottom on the isolation film 3a at least including the contact opening 2, an isolation film 3b which selectively has a through hole opening 7 therein and a second layer wiring made of gold 4, which has titanium-tungsten 6 at its bottom, on the isolation layer 3b at least including the through hole opening 7. The isolation layer 3b selectively having the through hole opening 7 and the wiring thereon are repeatedly formed until a desired number of wiring layers is reached and an isolation film 3c for covering is provided on the top layer wiring. In this case, wiring materials include aluminum and aluminum alloy having titanium-tungsten at its bottom, in addition to gold having titanium-tungsten at its bottom as shown in this example.
Materials of isolation films 3a, 3b and 3c are as follows.
A silicon oxide film formed by the CVD method or a plasma method is often used as an isolation film on the semiconductor substrate 1. An inorganic isolation film such as silicon oxide film formed by the plasma CVD method or an organic or inorganic coating film or a type of structure which is formed by compositely multi-layering these films are often used as an inter-layer isolation film including the wiring and others thereon. In addition, an organic coating film such as polyimide is often used as the uppermost covering isolation film.
Near-the-surface and internal portions of the main material of the wiring are made of the same kind of metal.
Since both surface and internal portions of the wiring of semiconductor devices having the above described conventional wiring structure are made of the same metal, a high frequency current which flows through the wiring intensively flows near the surface of the wiring due to the surface effect when the semiconductor devices are operated with a high frequency and therefore there have been problems that the current inside the wiring reduces, the apparent cross section also reduces, and the wiring resistance increases, thus causing the semiconductor devices to be unsuitable for a high speed operation.